Production of acetals



Patented Oct. 19, 1948 PRODUCTION OF ACETALS Heinz lleinemann, UpperDarby, Pa., assignor to Porocel Corporation, Philadelphia, Pa., a corporation of Delaware No Drawing. Application February 26, 1946,

, Serial No. 650,393

1 (c1. zoo-s15) I The present invention relates to the production ofacetals by the reaction of an alcohol with an aldehyde in the presenceof an argillaceous adsorbent.

In accordance with the present invention, a mixture of an alcohol and analdehyde is brought into contact with an argillaceous adsorbent underconditions promoting the formation of an aoetal, and the acetal andunconverted reactants are separated from the adsorbent. The acetal andthe unconverted reactants are separated by fractional distillation, andthe adsorbent, when spent, is reactivated simply by heating, or bysteaming and then heating.

The acetals produced in accordance with the present invention maygenerally be represented by the formula:

RCH

where B. may be hydrogen, alkyl, or aryl radicals, and R1 and R2 may besimilar or dissimilar alkyl or aryl radicals.

The alcohols which may be employed include the lower aliphatic alcoholssuch as methyl alcohol, ethyl alcohol, propyl alcohol, isopropylalcohol, the butyl alcohols, and the amyl alcohols. Higher homologues ofthis series may also be used, provided such alcohols are liquid, or maybe rendered liquid under the conversion conditions, i. e., by admixturewith dry, inert diluents, or by the solvent action of the aldehyde usedor the acetal formed. The aliphatic polyhydric alcohols such as glycol,glycerol, diethylene glycol, and the polyglycols may also be used, aswell as the aromatic alcohols phenyl methanol, phenyl ethan01, phenylpropane], and the like.

The aldehydes which may be utilized in the present invention include thelower aliphatic aldehy'des such as formaldehyde, acetaldehyde,

,propional'clehyde, butyraldehyde, valeraldehyde,

2 water-attracting materials such as activated alumina, bauxite, fullersearth, bentonite, acid activated bentonite, synthetic calcium silicates,magnesium silicates, aluminum silicates, and sil ica gel. Thesematerials are preferably activated, by heating at a suitable temperatureto remove at least a portion of their water content. For example,hydrated alumina, bauxite, fullers earth, the bentonites, and thesynthetic silicates may be dried and calcined by heating at 600 F. to1200 F, for a period of time suflicient to reduce their volatile mattercontent (water) to about 7% by weight or less, and preferably 5% orless.

The acetal-forming reaction is carried out according to the presentinvention by contacting a mixture of the alcohol and the aldehyde withthe adsorbent under suitable conditions of temperature and time toobtain substantial yields of acetal without excessive side reactionsproductive of aldehyde polymers and other substances. Temperaturesbetween 0 C. and 50 C. have been found suitable, and excellentconversions are obtained between 15 C. and 30 C. Temperatures higherthan 50 C. may be used, but usually lead to the formation ofconsiderable amounts of ald'ehyde polymers. Since the conversion appearsto be markedly influenced by the time of contact with the adsorbent, itis desirable to maintain the space velocity or volume of charge pervolume of adsorbent per hour at 0.1 or lower. Space velocities between0.01 and 0.1 have been found satisfactory, velocities of 0.01 to 0.03giving the highest conversions. The mole ratio of alcohol to aldehyde istheoretically 2:1 for conversion to acetal. It has been found, however,that either a lower or higher ratio may be employed, and satisfactoryconversions have been obtained with either an excess of alcohol oraldehyde in the reactant mixture. In general, mole ratios of alcohol andaldehyde may range from 1:1 to 4:1, preference being had for a slightexcess of alcohol over that theoretically required. Y

In carryin out the reaction, the alcohol and aldehyde may be mixed inthe desired ratio and the mixture then contacted with the argillaceousadsorbent, provision bein made to control the temperature of reaction.In one modification of the process, the reactant mixture may bepercolated or filtered through a bed of activated adsorbent at acontrolled temperature and rate, the,

8,451,949 s 4 tor a sumcient period of time to elect the desired Theproperties of the acetals obtained as above 7 conversion. The adsorbentis thereafter removed described are compared below with those reportedfrom the reactant mixture by settling, filtration, in the literature.Such comparison reveals that or centrifuging.-and may be regenerated byheatthe acetals prepared by the method of the present ing, or steamingi'ollowed by heating, In the 5 invention substantially duplicated thepure acepercolation technique, the now of reactants is tals of the priorart.

Boiling Dem", ldoleuihr mutt. Formula Point 0. Wt.

Exp. Lit. Exp. Lit. Lit.

Eflll m. ..o OCH; 1 24. 7 meta; azaleas}; .t is .ita if ii: iii

continued until the efllciency oi the adsorbent I claim: decreases to acommercially uninteresting level, 1. The method of producing an acetal,which at which time the supply of reactants is disconcomprises reactingan alcohol with an aldehyde tinned, the adsorbent bed i drained, theadsorb-'- in the presence of a naturally occurring argiient is strippedof reactants by steaming or washlaceous adsorbent which has beenthermally acing, and is then reactivated by heating at tempertivated.

atures, for example, between 300 F. and 12009.1 2. The method ofproducing Zen acetal, which The reactant mixture obtained by either ofthe comprises reacting an alcohol with an aldehyde above procedures maythereafter be separated in the presence of thermally activated bauxite.into components by fractionation, the acetal 3. The method of producingan acetal, which being delivered to storage and the unconvertedcomprises reacting an alcohol with an aldehyde in alcohol or aldehydebeing recycled for further the presence of thermally activated 'Iullersearth.

conversion. Where one or both of the reactants 4. The method ofproducing an acetal, which are gaseous or excessively volatile under thecon comprises reacting an alcohol with an aldehyde version conditions,asuperatmospheric pressure in the presence oi! thermally activatedbentonite. may be imposed upon the reaction system to pre- 4 5. Themethod of producing an acetal, which vent the lass of the reactants.Since the iormacomprises contacting a mixture of ethyl alcoholtion orthe acetal involves the condensation oi and acetaldehyde with activatedbauxite at a 1 mole of aldehyde with 2 moles of alcohol, and temperaturebetween 15 C. and 30v C. and at a consequent elimination of one mole ofwater, it space velocity of not more than 0.1.

is preferred to employ anhydrous or substantially 6. The method ofproducing an acetal, which dry reactants. However, the process of theprescomprises contacting a mixture of ethyl alcohol ent invention may beapplied to reactants conand propionaldehyde with activated bauxite at a.taining a small percentage of water, but the contemperature between 15C. and 30 C. and at a version is of course somewhat less eflective than40 space velocity 01 not more than 0.1. with dry reactants. I 7. Themethod of producing an acetal, which '-The present invention may befurther illuscompri s contacting a mixture of ethyl alcohol trated bythe following examples, which, however, and but aldehyde with activatedbauxite at a are not to be construed as limiting the scope temperaturebetween 15 C. and 30 C. and at 9.

thereof. space velocity of not more than 0.1.

600 volumes of 30/60 mesh bauxite which has been activated by heating at1200" F, to a vola- I EINZ W,

the matter content of 2% by weight was charged to an elongated reactionchamber, and a mix- REFERENCES CITED 'ture of aldehyde and alcohol'wassupplied to T fonowm f n top of the chamber and permitted to percolate mof this 5, ere Ce are f record m the downwardly through the bed 01adsorbent at a I a controlled rate and temperature. The eiliuent UNITEDSTATES PATENTS from the chamber was then fractionally distilled N b N tto recover the acetal from unconverted aldehyde, 55 1,312,1 King t 1 Aug5 1919 alcohol, and polymers. The results obtained are 1, 50, 3 m t 22:1932 given in the following/lia 2,161,066 La Lande June 6, 1939 3,328.3?Engel July 16, 1940 M018 B u s v P C t 1 0,3 0 Gresham June 6, Remain539g, '1? val 32, E1 35 2,382,874 Gresham Aug. 14, 1945 OTHER REFERENCESV Ethyl aleohol+ Berkman et al., Catalysis," pages 549 to 552 355951 9112:! 1a 0.01 a is and 735 to 741 (1940) Do..- 2:1 1 15 0.03 a so Do...2:1 0.02 a a: Do... 1:1 75 0.03 a 60 Ethyl alcohol-l- Butyraldehyda- 2:175 cos a 42

